Szkukalek A, Myslinski E, Mougin A, Luhrmann R, Branlant C
Laboratoire d'Enzymologie et de Génie Génétique, URA-CNRS 457, Université de Nancy I, Faculté des Sciences, Vandoeuvre-les-Nancy, France.
Biochimie. 1995;77(1-2):16-21. doi: 10.1016/0300-9084(96)88099-0.
In order to study the phylogenetic conservation of modified nucleotides in the spliceosomal U5 snRNA, we determined the nucleotide sequences of the U5 snRNAs from the slime mold Physarum polycephalum (EMBL data bank accession numbers: X74440 and X74441) and we identified the pseudouridine and 2'-O-methylated residues. From a comparison of all the U5 snRNAs studied at the level of nucleotide modifications, we concluded that the modified nucleotides in U5 snRNA can be divided into three classes according to their degree of conservation: i) the modified nucleotides of the 5' terminal cap structure that display some variations from one species to the other; ii) the modified nucleotides located in the helical part of the stem/loop structure I that vary greatly in number, position and identity from one species to the other; and iii) the modified nucleotides of the terminal loop 1, that are almost identical in all the species studied. Taking into account the recent discovery of a crucial role played by this terminal loop of U5 snRNA in 5' and 3' splice site definition, we postulate that the numerous modified nucleotides it contains, five out of a total of 11, play an important role in spliceosome assembly and function. Their possible role is discussed.
为了研究剪接体U5小核仁RNA（snRNA）中修饰核苷酸的系统发育保守性，我们测定了黏菌多头绒泡菌U5 snRNA的核苷酸序列（EMBL数据库登录号：X74440和X74441），并鉴定了假尿苷和2'-O-甲基化残基。通过在核苷酸修饰水平上对所有研究的U5 snRNA进行比较，我们得出结论，U5 snRNA中的修饰核苷酸可根据其保守程度分为三类：i）5'末端帽结构的修饰核苷酸，在不同物种间存在一些差异；ii）位于茎环结构I螺旋部分的修饰核苷酸，其数量、位置和种类在不同物种间差异很大；iii）末端环1的修饰核苷酸，在所有研究的物种中几乎相同。考虑到最近发现U5 snRNA的这个末端环在5'和3'剪接位点定义中起关键作用，我们推测它所含的众多修饰核苷酸（总共11个中有5个）在剪接体组装和功能中起重要作用。文中讨论了它们可能的作用。
